headers reflect variations of the host name not the senders domain (except DKIM is providing the hosted domains key)123.comwww.123.commail.123.combut still reflects xxx.xxx.xxx.22 even though all mail MX records for hostname and hosted domains name point to: xxx.xxx.xxx.23

1. Which conf files do I set the mail.123.com name in?2. how can I get mail/smtp outgoing to reflect the hosted domains name not the servers name?3. how can I get the smtp to use the Ip set in DNWS mx records not the servers IP assigned to apache?